enzymes

Question 1

what are enzymes?

Answer 1

enzymes are tertiary, globular proteins. they are biological catalysts regulating biological processes in living organisms.

Question 2

what determines an enzyme’s specific function?

Answer 2

it is the protein nature and tertiary structure of an enzyme that determines its specific function.

Question 3

describe how enzymes lower activation energy? (4)

Answer 3

• an important feature of enzymes is their action in lowering the activation energy
• the activation energy is the energy required for chemical reactions to take place
• by lowering the activation energy the rate of reaction is increased
• enzymes lower the activation energy through the formation of enzyme-substrate complexes

Question 4

draw a graph of how enzymes lower activation energy

Answer 4

see graph

Question 5

what is a key feature of enzymes?

Answer 5

enzymes are specific. some enzymes e.g. amylase act on a single substrate, others such as lipases show a clear specificity for particular chemical bonds.

Question 6

enzyme specificity is a feature of the ______ ________ _________ of an enzyme

Answer 6

enzyme specificity is a feature of the unique tertiary structure of an enzyme

Question 7

what is an enzyme’s ______ ________ structure held together by? what does this determine?

Answer 7

• unique tertiary
• this structure is held together by hydrogen bonds, ionic bonds and sometimes disulfide bridges
• this determines the shape (configuration) and electrostatic charges of the active site

Question 8

describe the lock and key model (4)

Answer 8

• the active site represents a small region of the enzyme molecule
• only substrates with the complementary shape to the active site will bind to it forming an enzyme-substrate complex
• the reaction takes place and the product is released from the active site
• the enzyme remains unchanged at the end of the reaction

Question 9

draw a diagram of the lock and key model

Answer 9

see diagram

Question 10

describe the induced fit model (5)

Answer 10

this suggests that the active site of an enzyme can change its shape slightly

this occurs in the presence of the correct substrate enabling the substrate to combine at the active site of the enzyme

the enzyme is flexible and moulds itself around the substrate (similar to a glove moulds itself to the shape of a hand)

• the substrate interacts with the active site and causes the enzyme to change shape
• the active site may allow two molecules to come very close together making a reaction more likely e.g. condensation